Polymer-coated substrates are used in many technological applications. For example, implantable medical devices can be coated with biologically inert polymers. In another example, polymer coated substrates are used for the preparation and/or analysis of biological molecules. Molecular analyses, such as certain nucleic acid sequencing methods, rely on the attachment of nucleic acid strands to a polymer-coated surface of a substrate. The sequences of the attached nucleic acid strands can then be determined by a number of different methods that are well known in the art.
In certain sequencing-by-synthesis processes, one or more surfaces of a flow cell are coated with a polymer to which nucleic acids are attached. The current procedure used to coat flow cells involves transferring a polymerizing mix into channels on the flow cell and incubating for a fixed time period. This procedure is simple and results in reliable coatings that are consistently able to support all downstream chemical processing steps including bridge amplification and sequencing.
There are, however, several limitations to many of the currently-used surface polymer coatings. For example, (i) some of the current approaches limit the methods that can be used to coat surfaces because air-sensitive polymer mix is required; (ii) some of the formed coatings have to be stored in a “wet” state, for example, in aqueous solution; and (iii) grafting conditions often need to be optimized in order to avoid intensity gradients.
In addition, there is also a need to create patterned flowcells with defined features periodically spaced. One method of creating patterned flowcells is to chemically modify a bead, and then apply that bead to a pre-arrayed surface with the surface containing open wells which can accommodate the beads. The beads can be coated with a polymer that can support cluster-growth based sequencing prior to loading them into the wells. Polymer coatings that are useful on planar array surfaces may not be convenient for coating beads due to aggregation caused by the coating and requirements to store the beads in aqueous buffers after coating. This results in some limitations in commercial applications. Accordingly, there is a need for new polymer coatings that do not suffer from one or more of the disadvantages of current polymer coatings when used to coat beads.